        .header {
            width: 100%;
            height: 60px;
            line-height: 60px;
            background-color: skyblue;
            color: #fff;
            position: fixed;
            top: 0;
            left: 0;
            z-index: 999;
        }
        
        .header-wrapper {
            width: 1200px;
            margin: 0 auto;
            height: 100%;
            display: flex;
            justify-content: space-around;
            align-items: center;
        }
        
        .header-wrapper>li>a {
            color: #fff;
        }
        
        .container {
            margin-top: 160px;
            height: 100%;
        }
        
        .example-classify-wrapper li {
            background: #ccc;
        }
        
        .container>.nav-wrapper {
            height: 100%;
            width: 200px;
            background-color: skyblue;
            float: left;
            position: fixed;
            left: 0;
            top: 60px;
            overflow: auto;
        }
        
        h3 {
            height: 50px;
            line-height: 50px;
            text-align: center;
            color: #333;
            border-bottom: 1px solid #ccc;
            cursor: pointer;
        }
        
        .content-wrapper {
            margin-left: 200px;
            width: calc(100% - 200px);
            padding: 50px;
            box-sizing: border-box;
        }
        
        h3+ul {
            display: none;
        }
        
        ul.on {
            display: block;
        }
        
        h3+ul>li {
            height: 40px;
            line-height: 40px;
            border-bottom: 1px solid #fff;
            text-align: center;
        }
        
        .return-top {
            width: 80px;
            height: 80px;
            font-size: 20px;
            color: #fff;
            background-color: skyblue;
            position: fixed;
            right: 10px;
            bottom: 10px;
            display: none;
            cursor: pointer;
            border-radius: 30%;
        }
        
        .return-top-inner {
            height: 100%;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
        }
        
        .return-top span {
            display: block;
            text-align: center;
        }